The proposed work attempts to characterize in a biochemical and morphological approach cardiac cells isolated from the adult rat in order to be used as in vitro models of cardiac metabolism. Changes in glucose uptake and metabolism in cells from normal and diabetic animals, in response to insulin, will be correlated with binding experiments designed to determine changes in receptor population, affinity constants, and possible compartmentalization of insulin. The possible effects of insulin on calcium transport will also be investigated. An attempt will be made to determine if changes in calcium transport reflect increases in calcium flux or total cell ion. The contribution of the Na/K ATPase and, in particular, potassium levels on calcium fluxes will be determined. Molecular effects of insulin on certain soluble proteins and vice-versa will be assessed in the hope that it may provide information concerning presence of a "second messenger". Finally as part of this project, the events regulating cardiac contractility at the cellular level will be investigated with the combined techniques differential-interference contrast microscopy, fluorescence microscopy and closed-circuit video monitor in association with biochemical events regulating ion transport and muscle mechanics.